Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media

Abstract

In this review article, authors presented up to date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment / plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here, the authors, first presented the compilation on insitu colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role on inorganic and organic contaminants transport in porous media. This review article is superior over last two review articles by Elimelech and Ryan [3] and Kretzschmar et al. [6] respectively as (i) It gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviewed the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon is also depends on various factors such as concentration of colloidal fines, superficial velocity and bead to particle size ratio. This plugging-based contaminant transport can be used to develop in containment technique in soil and groundwater remediation. (ii) It also presented the importance of “critical salt concentration (CSC)”, “critical ionic strength for mixed salt, “critical shear stress” or “critical particle concentration (CPC)” on insitu colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) This also reviewed the another class of colloidal fines called “biocolloids” and their transport in porous media. Finally authors are highlighted the future research based on their critical review on colloid-associated contaminant transport in saturated porous media.